Various communications systems are used to allow electronic devices such as computers to communicate and exchange data and other types of information. For example, various systems such as Local Area Networks (“LANs”), the Internet and conventional telephone networks often link computers. A particularly effective method to allow mobile computers to communicate is with a Wireless Local Area Network (“WLAN”). A very popular and pervasive WLAN system is that specified by the IEEE 802.11 wireless networking standard, referred to henceforth in this document simply as the 802.11 standard, an industry protocol that has successfully resolved many interoperability issues among the manufacturers of WLAN equipment. The 802.11 standard specifies several distinct OSI Physical (“PHY”) Layer radio transmission mechanisms whereby signals may be transmitted over the wireless medium, as well as a single Medium Access Control (“MAC”) layer that organizes and controls the exchange of data packets or datagrams between the communicating stations. This IEEE 802.11-19979 MAC, henceforth referred simply as the 802.11 MAC, also supports mechanisms whereby special IEEE 802.11 compliant wireless stations, henceforth referred to simply as 802.11 stations, called Access Points (“APs”) also connect to a wired LAN, to then in many occasions traverse said LAN and access the broader Internet. Mobile computers connect to the Access Points wirelessly using 802.11 WLAN Network Interface Cards (“NICs”) that plug in to their standard computer I/O connections (such as USB, PCI or CardBus).
Two specific IEEE 802.11 PHY standards (specifically. IEEE 802.11a and IEEE 802.11b, henceforth called 802.11a and 802.11b, respectively) have gained overwhelming worldwide acceptance. The 11 Mbps 802.11b PHY, operating at 2.4 GHz and employing Complementary Code Keying (“CCK”) single carrier QPSK modulation, has been shipped in millions of NICs and APs since 1999. The 54 Mbps 802.11a PHY, operating in the 5 GHz band and based on multiple carrier Orthogonal Frequency Division Multiplex (“OFDM”) signaling, is, on the other hand, rapidly gaining wide acceptance for large company WLAN deployments. To complicate matters further, the IEEE is standardizing a combined CCK and OFDM-based extension to the 2.4 GHz 802.11b PHY called IEEE 802.11g, currently in draft form and henceforth referred to as 802.11g, and corresponding combined 802.11b and 802.11g, or “802.11b/g” IC and software technology, and products have begun to ship.
One emerging, popular approach is to use dual band, multiple protocol WLAN equipment. Some IC vendors have begun to ship “802.11abg” chipsets and associated software that enable wireless stations to transmit and receive using either 802.11a or 802.11b/g on a datagram by datagram basis. This technology is presently being used to manufacture “Multiprotocol NICs” (“MPNICs”) that can auto-negotiate and communicate with an AP using either 802.11b. 802.11g or 802.11a at any given time. As an important note, these new “multilingual” NICs also incorporate the exact 802.11-1997 MAC protocols in order to not confuse any legacy devices with which they would communicate.
Legacy (single band, single protocol) APs currently, are nearly 100% 802.11b-based and can only communicate using CCK at 2.4 GHz. “Dual Single Protocol APs” (“DSPAPs”, consisting of two individual 802.11a and 802.11b APs in one enclosure sharing a common Ethernet connection to the LAN distribution system) however, are now being manufactured that can, effectively, simultaneously “talk” CCK at 2.4 GHz and OFDM at 5 GHz, again using the common 802.11-1997 MAC.
The evolution from 2.4 GHz CCK-based 802.11b technology to 5 GHz OFDM 802.11a-based equipment, therefore, involves serious, compatibility, interoperability and legacy support issues, and both WLAN equipment manufacturers and systems deployers are still grappling with how best to resolve them.
Once such a “single 802.11abg radio, earns 802.11 MAC” Multiprotocol Access Point (“MPAP”) proves feasible, a new type of AP-like device that takes advantage of both the frequency agility and the Multiprotocol capabilities of the MPAP technology also becomes viable, if nat compelling. This new device a “Multiprotocol Repeater” (“MPR”) replaces the MPAP's wired LAN connection with an(other) 802.11a or 802.11b/g link that would, in turn, communicate with an “upstream” MPAP provisioned wit the actual connection to the wired LAN or Internet. Multiple protocol repeaters could be implemented using three or four (!) distinct legacy single protocol 802.11a and 802.11b/g APs, but the invention documented herein provides for implementation of MPR devices that specifically make use of 802.11abg radio technology to provide significantly reduced cost and complexity.
While the above solution works acceptably well, it is a very costly disadvantage to require incorporation of two independent single protocol APs (incorporating separate 802.11a and 802.11b/g radios and MAC processors, and incurring much duplication of costly support circuitry) in order to produce a single dual protocol AP. It would be much more cost-effective to utilize a single 802.11abg-capable radio device for these new “802.11a plus 802.11b/g” APs as well. And of course, it is essential that any such devices incorporate the 802.11-1997 MAC unchanged. The present invention accomplishes all these objectives.
In the above fashion the new MPNICs can communicate with the common legacy 802.11b-only AN, the newer (and very rare) 802.11a-only APs or the increasingly popular “802.11a plus 802.11b/g” dual protocol DSPAPs. Similarly, those DSPAPs can communicate with the overwhelmingly predominant 802.11b-only legacy NiCs, the (relatively rare) newer 802.11a-only NICs and the “802.11a, b or g” MPNICs.